The present invention relates to an image display and a method of manufacturing the same, and particularly to a technology effective for application to a display apparatus which has thin-film electron emitters having an electrode-insulator-electrode structure to emit electrons into vacuum.
The thin-film electron emitters are electron-emitter elements each using hot electrons produced by applying a high electric field to an insulator.
As a typical example, an MIM (Metal-Insulator-Metal) electron emitter comprising a thin film having a three-layer structure of a top electrode-insulating layer-base electrode will be explained.
FIG. 14 is a diagram for describing the principle of operation of an MIM electron emitter illustrated as a typical example of a thin-film electron emitter.
A driving voltage is applied between a top electrode 11 and a base electrode 13 to set an electric field within a tunneling insulator 12 to 1 MV/cm to 10 MV/cm and over. Thus, electrons placed in the neighborhood of the Fermi level in the base electrode 13 are transmitted through a barrier by tunneling phenomena. Thereafter, they are injected into the conduction bands of the tunneling insulator 12 and top electrode 11, thereby resulting in hot electrons.
Some of these hot electrons are subjected to scattering under interaction with a solid in the tunneling insulator 12 and the top electrode 11, thus leading to the loss of energy.
As a result, hot electrons having various energies exist when they have reached an interface between the top electrode 11 and vacuum 10.
Of these hot electrons, ones having energy larger than the work function φ of the top electrode 11 are emitted into the vacuum 10, and ones other than the above ones flow into the top electrode 11.
Assuming that a current based on the electrons flowing from the base electrode 13 to the top electrode 11, is called a diode current (Id), and a current based on the electrons emitted into the vacuum 10 is called an emission current (Ie), an electron emission efficiency (Ie/Id) ranges from about 1/103 to about 1/105.
Incidentally, the MIM thin-film electron emitter has been described in, for example, Japanese Patent Application Laid-Open No. Hei 9-320456.
Now, the top electrode 11 and the base electrode 13 are provided in plural form and these plural top electrodes 11 and base electrodes 13 are formed orthogonal to one another to thereby form thin-film electron emitters in matrix form. Consequently, electron beams can be produced from arbitrary locations and hence they can be used as electron emitters for a display apparatus.
Namely, a display apparatus can be constructed wherein thin-film electron-emitter elements are placed at every pixel, and electrons emitted therefrom are accelerated in vacuo and thereafter applied to each of phosphors to thereby allow the applied phosphor to emit light, whereby a desired image is displayed thereon.
The thin-film electron emitters have excellent features as electron-emitter elements for the display apparatus in that they are capable of implementing a high-resolution display apparatus because the emitted electron beams are excellent in directionality, and they are easy to handle because they are insusceptible to the influence of their surface contamination, for example.
In the display apparatus using the conventional thin-film electron emitters, when one of a large number of thin-film electron-emitter elements (electron emission regions) placed in matrix form was short-circuited due to a failure in manufacture thereof or other reasons, no electrons were emitted from all the thin-film electron-emitter elements on a row or/and a column to which such a thin-film electron-emitter element was connected, thus causing no light emission. Namely, a “point defect” of one thin-film electron-emitter element has caused a “line defect”.
The above-described point will be explained below.
FIG. 15 is a diagram showing a schematic configuration of a conventional thin-film electron-emitter matrix.
Thin-film electron-emitter elements 301 are respectively formed at points where row electrodes (base electrodes) 310 and column electrodes (top electrodes) 311 intersect respectively.
Incidentally, while the thin-film electron-emitter matrix is illustrated with 3 rows and 3 columns in FIG. 15, the thin-film electron-emitter elements 301 are actually placed by the number of pixels constituting a display apparatus, or the number of sub-pixels in the case of a color display apparatus.
Now, the respective thin-film electron-emitter elements 301 are directly connected to the row electrodes 310 and the column electrodes 311 respectively.
Therefore, when, for example, a thin-film electron-emitter element 301 placed at an intersection (R2, C2) of a row electrode 310 of R2 and a column electrode 311 of C2 is short-circuited due to a failure in manufacture thereof or the like, the row electrode 310 of R2 and the column electrode 311 of C2 are short-circuited. Hence even if an attempt were made to apply a suitable voltage to both electrodes from a row electrode driving circuit 41 or a column electrode driving circuit 42, the voltage would not be applied thereto.
Therefore, all the thin-film electron-emitter elements 301 on the row electrode of R2, or/and all the thin-film electron-emitter elements 301 on the column electrode 311 of C2 are not operated, thus causing a “line defect”.
Even if elements equivalent to about 1/10000 of the total number of pixels have “point defects” in a matrix-type display apparatus such as a liquid-crystal display apparatus or the like, no problem occurs from a practical standpoint and they can be used in most cases.
Namely, about 100 “point defects” can be allowed in the case of a display apparatus configured in 480×640×3 dots, for example.
However, one having a “line defect” such as non-light emission of all elements on one line cannot be used as a display apparatus.
Thus, the display apparatus using the conventional thin-film electron emitters was accompanied by a problem that the “point defects” produced the “line defect”, thereby reducing production yields.